1. Technical Field
Embodiments of this disclosure relate to a charging device that causes a charger to contact or come close to a surface of a latent image bearer and charges the surface of the latent image bearer. In addition, embodiments of this disclosure relate to an image forming apparatus such as a copy machine, a facsimile, and a printer that charges the latent image bearer serving as a charging target with the charging device.
2. Description of the Related Art
Image forming apparatuses are used as, for example, copiers, printers, facsimile machines, and multi-functional devices having at least one of the foregoing capabilities. Such an image forming apparatus may include a charging device to charge a photoconductor serving as a latent image bearer. As the charging device, for example, a contact charging device or a proximity charging device is known that causes a charger to contact or come close to a photoconductor to be a latent image bearer, applies a voltage to the charger, and charges the photoconductor. The charger includes, for example, a roller, a brush, or a blade and generates discharge between the charger and the photoconductor directly to charge the photoconductor.
The contact charging device or the proximity charging device uses, for example, a method (hereinafter, referred to as an “alternating current (AC) superimposing method”) of applying an alternating voltage obtained by superimposing a pulsating voltage on a direct-current voltage to the charger. In the AC superimposing method, discharge (hereinafter, referred to as “normal discharge”) from the charger to the photoconductor is generated and discharge (hereinafter, referred to as “reverse discharge”) from the photoconductor to the charger is generated. The normal discharge and the reverse discharge are repeated several times, so that a charging state on a surface of a photoconductor drum becomes uniform gradually, and the charging unevenness is removed.
In addition, to suppress an amount of generation of discharge products in the AC superimposing method, for example, a technology prevents generation of the reverse discharge not contributing to charging of the photoconductor to reduce an amount of generation of ozone. Another technology decreases a discharge current amount to suppress an amount of generation of NOx, focusing on that the amount of generation of NOx at the time of the discharge is proportional to the discharge current amount from the charging device.